XCF, short for eXperimental Computing Facility,[1] is the native image format of the GIMP image-editing program. It saves all of the data the program handles related to the image, including among others each layer, the current selection, channels, transparency, paths and guides.

The saved image data are compressed only by a simple RLE algorithm, but GIMP supports compressed files, using either gzip or bzip2. The compressed files can be opened as normal image files.

The XCF file format is backward compatible (all versions of GIMP can open earlier versions' files) and in some cases, forward compatible. For example, GIMP 2.0 can save text in text layers while GIMP 1.2 can not. Text layers saved in GIMP 2.0 will open as ordinary image layers in GIMP 1.2. However, XCF files containing layer groups, a feature introduced in GIMP 2.7, can't be opened with GIMP 2.6.

The use of XCF as a data interchange format is not recommended by the GIMP developers,[2] since the format reflects the GIMP's internal data structures, and there may be minor format changes in future versions. A collaborative effort between the GIMP developers and Krita developers is underway to design a raster file format called OpenRaster, modelled on the OpenDocument format, for use in both applications in a future version.

As of GIMP version 2.8 images are loaded and imported in XCF format. GIMP only supports saving in XCF format; other formats have been moved to the Export dialog.

CinePaint is a fork of the GIMP with support for 16 bit and 32 bit floating point channels, and 16 bit integer channels. The XCF file format used in CinePaint has diverged from the GIMP's native format, so XCF files created in the GIMP cannot be opened in Cinepaint, and vice versa.

Some image viewers and conversion software can read the format with varying degrees of success: